<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  
  <div id="app"></div>

  <template id="my-app">
    <h2>{{message}}</h2>
    <component-a></component-a>
  </template>

  <template id="component-a">
    <h2>我是组件A</h2>
    <p>我是内容, 哈哈哈哈</p>
  </template>

  <script src="../js/vue.js"></script>
  <script>

    const ComponentA = {
      template: "#component-a"
    }


    const App = {
      template: '#my-app',
      components: {
        // key: 组件名称
        // value: 组件对象
        ComponentA: ComponentA
      },
      data() {
        return {
          message: "Hello World"
        }
      }
    }

    const app = Vue.createApp(App);
    // app.component("ComponentA", ComponentA);
    app.mount('#app');
  </script>
</body>
</html>